OnceCell on Metadata

rust-lang · Dec 13, 2023 · d348f3a · d348f3a
1 parent 879468b
commit d348f3a
Showing 1 changed file with 10 additions and 3 deletions.
diff --git a/analyzeme/src/profiling_data.rs b/analyzeme/src/profiling_data.rs
@@ -7,6 +7,7 @@ use measureme::file_header::{
 use measureme::{
     EventId, PageTag, RawEvent, SerializationSink, SerializationSinkBuilder, StringTableBuilder,
 };
+use std::cell::OnceCell;
 use std::fs;
 use std::path::Path;
 use std::sync::Arc;
@@ -15,6 +16,7 @@ use std::{error::Error, path::PathBuf};
 #[derive(Debug)]
 pub struct ProfilingData {
     event_decoder: Box<dyn EventDecoder>,
+    metadata: OnceCell<Metadata>,
 }
 
 impl ProfilingData {
@@ -84,11 +86,15 @@ impl ProfilingData {
             }
         };
 
-        Ok(ProfilingData { event_decoder })
+        Ok(ProfilingData {
+            event_decoder,
+            metadata: OnceCell::new(),
+        })
     }
 
-    pub fn metadata(&self) -> Metadata {
-        self.event_decoder.metadata()
+    pub fn metadata(&self) -> &Metadata {
+        // Cache the metadata during the first access
+        self.metadata.get_or_init(|| self.event_decoder.metadata())
     }
 
     pub fn iter<'a>(&'a self) -> ProfilerEventIterator<'a> {
@@ -302,6 +308,7 @@ impl ProfilingDataBuilder {
                 )
                 .unwrap(),
             ),
+            metadata: OnceCell::new(),
         }
     }